The engine mounted on vehicles or the like is provided with a driving valve system, auxiliary machines, an oil pressure control device and other similar devices. Oil discharged from an oil pump is supplied through respective oil passages to these devices or systems for lubrication, operation and control thereof.
Such an oil passage construction for an engine with an oil pressure control device as described above is shown in FIGS. 7 and 8. In FIG. 7, reference numeral 102 designates an engine with an oil pressure control device (hereinafter referred to as "an engine"), 104 a cylinder block, 106 a lower case, 108 an oil pan, 110 a cylinder head, 112 a head cover, and 114 a chain case. In the engine 102, a crank shaft 116 is provided on the cylinder block 104, and intake and exhaust cam shafts 118, 120 for driving intake and exhaust valves (not shown) in the driving valve system are supported on the cylinder head 110.
In the intake and exhaust cam shafts 118, 120, intake and exhaust journal portions 122, 124 are supported on cam shaft bearings 126, 128 of the cylinder head 110 by intake and exhaust cam shaft caps 130, 132.
The engine 102 is provided with an oil pump 134 driven by the crank shaft 116, a chain tensioner 136 as an auxiliary machine for imparting tension to a timing chain (not shown) which acts as a driving force transmitting unit for a driving valve for transmitting rotation of the crank shaft 116 to the intake and exhaust cam shafts 118, 120, and an oil control valve 140 of a variable valve timing device 138 as an oil pressure control device.
In the oil passage construction for the engine 102, an oil passage 142 is provided on the block side to which oil discharged by the oil pump 134 is supplied, and a throttle portion 144 is provided on the oil passage 142 on the block side. Oil controlled in amount by the throttle portion 144 on the block side is supplied to an oil passage 146 provided in the cylinder head 106.
FIG. 8 illustrates an oil passage 148 for supplying oil for a driving valve system to the intake and exhaust journal portions 122, 124 of the respective intake and exhaust cam shafts 118, 120, an oil passage 150 for supplying oil to auxiliary machines such as the chain tensioner 136, and a controlling oil passage 152 for supplying controlling oil to the oil control valve 140 of the variable valve timing device 138. The aforementioned passages branch from or communicate with the head-side oil passage 146.
The oil passage 148 for the driving valve system branches into oil passages 154, 156 for the respective intake and exhaust cam shafts to supply oil to the intake and exhaust cam shaft caps 130, 132 to lubricate the intake and exhaust journal portions 122, 124. The oil passage 150 supplies oil to the chain tensioner 136 to actuate a plunger (not shown) to apply tension to the timing chain.
The controlling oil passage 152 supplies controlling oil to the oil control valve 140. The operation of the oil control valve 140 is controlled by control means (not shown) so as to supply controlling oil to a hydraulic actuator 162 provided on one end of the intake cam shaft 118 via an advance angle oil passage 158 and a delay angle oil passage 160, so that the phase of the intake cam shaft 118 relative to the crank shaft 116 can be changed to vary valve timing of the intake and exhaust valve.
The oil passage construction for an engine with an oil pressure control device as described above is disclosed in Japanese Utility Model Application Laid-Open No. 61-179312, Japanese Patent Application Laid-Open No. 5-171904, Japanese Patent Application Laid-Open No. 5-288022, Japanese Patent Application Laid-Open No. 9-79019, Japanese Patent Application Laid-Open No. 9-170415, Japanese Patent Application Laid-Open No. 9-170416, and Japanese Patent Application Laid-Open No. 10-30418.
Japanese Utility Model Application Laid-Open 61-179312 discloses-an orifice for controlling the oil amount which is provided in an oil supply passage for supplying oil to a driving valve mechanism. Japanese Patent Application Laid-Open No. 5-171904, Japanese Patent Application Laid-Open No. 5-288022, Japanese Patent Application Laid-Open No. 9-79019, Japanese Patent Application Laid-Open No. 9-170415, Japanese Patent Application Laid-Open No. 9-170416, and Japanese Patent Application Laid-Open No. 10-30418 are all concerned with the passage construction in which an oil control valve for supplying advance angle oil and delay angle oil to a hydraulic actuator of a variable valve timing device is provided on one end of a cam shaft to provide an advance angle oil passage and a delay angle oil passage for advance angle oil and delay angle oil, respectively.
In the oil passage construction shown in FIGS. 7 and 8, the throttle portion 144 is provided in the oil passage 142 on the block side, and the quantity of oil supplied to the oil passage 146 on the head side is controlled by the throttle portion 144 to thereby ensure that an adequate amount of oil is supplied for lubrication of the crank shaft 116. However, in the oil passage construction shown in FIGS. 7 and 8, since the amount of oil supplied to the oil passage 146 on the head side is controlled, the controlling oil amount supplied to the oil control valve 140 is also limited and reduced. This poses an inconvenience in that the responsiveness of the hydraulic actuator 162 controlled by the oil control valve 140 decreases.
Such an inconvenience as described above can be overcome by removing the throttle portion 144 on the block side. However, the removal of the throttle portion 144 on the block side not only results in an inconvenience as to the quantity of oil supplied for lubrication of the crank shaft 116, but also results in the inconvenience in that oil supplied to the oil passage 146 on the head side is supplied to the intake and exhaust cam shaft caps 130, 132 and the chain tensioner 134 in a greater amount than is necessary and as a result, the controlling oil amount supplied to the oil control valve 140 fails to fulfill the necessary amount.
It is necessary for overcoming the inconveniences as described above to increase the discharge amount of the oil pump 134. However, this poses an inconvenience in that the oil pump 134 becomes large in size, and an inconvenience in that the mechanical loss of the engine 102 is increased due to the larger-size of the oil pump 134.